Tonometer



March 23, 1943. A, H, PARSQNS' 2,314,514

TONOMETER Filed June 11, 1941 INVENTOR,

AT TORNEK WHHWM Patented Mar. 23, 1943 UNITED STATE. PATENT OFFICE TONOMETER Alfred H. Parsons, San Francisco, Calif.

Application June 11, 1941, Serial No. 397,639

10 Claims.

" an improved tonometer having novel means for readily determining the intraocular pressure of the eyeball.

Other and further objects of my invention will be pointed out hereinafter or will be indicated in the appended claims, or will be obvious to one skilled in the art upon an understanding of the present disclosure. For the purpose of this application, I have elected to show herein certain forms and details of a tonometer representative of my invention; it is to be understood, however, that the embodiments of my invention herein shown and described are for the purpose of illustration only, and that therefore it is not to be regarded as exhaustive of the variations of the invention, nor is it to be given an interpretation such as might have the effect of limiting the claims short of the true and most comprehensive scope of the-invention in the art.

In the accompanying drawing:

Fig. l is a front elevation of a tonometer embodying the preferred principles of my invention;

Fig. 2 is a side View of the same;

Fig. 3 is an enlarged front View of the instrument with the front cover plate removed, showing parts broken away and other parts in cross section;

Fig. 4 is a sectional view taken on the line 44 of Fig. 3; and

Fig. 5 is a sectional view taken on the line 5-5 of Fig. 3.

Referring to the drawing, the numeral l designates a suitably shaped casing having a front cover plate 2 detachably secured thereto. The cover plate has a suitable sight opening at its lower side which is closed by a window 3 having a vertical indicating mark 4 thereon.

Secured at their upper ends to the lower side of the casing are two parallel legs 5 having a block 6 attached to their lower ends. Slidably mounted on the legs 5 are sleeves l, and secured thereto as by welding is a channelled ring 8 which is substantially C-shaped in cross section. Rotatably mounted in the annular' channel of the ring 8 is a circular band 9 having oppositely disposed semi-circular finger pieces I!) secured thereto.

Slidably extending through aligned holes provided in the lower side of the casing l and in the block 5 is a rod ll having a detachable end piece l2 at its lower end and a pointed tip I3 at its upper end. The rod II slidably extends through suitable non-corrosive bearings [4 held in the aligned holes in the lower side of the easing and in the block 6. The rod H is positioned midway between the legs 5 and in substantially parallel relation thereto.

Secured as by an adhesive or other suitable means to a depending annular projection 6 on the block 6 is a tubular member I5 having an enlarged foot plate It at its lower end. The extreme lower ends of the end piece 12 and the foot plate 16 are each provided with suitable concave surfaces which in operation are adapted to be brought into engagement with the cornea of a person's eye being examined. The lower enlarged part of the rod ll extends through the opening in the tubular member l5 and neither it nor the end piece I 2 engages with the said tubular member or with the base plate It. The foot plate I 6, the tubular member l5 and the end piece I 2 are preferably made from a suitable transparent plastic material. The foot plate I6 being transparent permits the person conducting an eye examination to observe the exact position of the concave surface of the end piece l2 with respect to that part of the cornea positioned within the confines of the said base plate.

The rod H is suitably threaded at points above the block 6, and adjustably positioned thereon is a nut I! which serves the dual purpose of limiting the downward movement of the rod and the end piece l2 and the supporting of a suitable Weight l3. The weight [8, as well as others similar to it, are each provided with a radially disposed slot which permits the free passage therethrough of the rod II when the weight is placed on or removed from the supporting nut ll. The nut IT. is so adjustably positioned on the rod II as to permit the end piece l2 to be suspended so its concave surface extends at a predetermined distance beneath the concave surface of the foot plate 16, as indicated in Fig. 3.

Attached, as by screws Hi, to the rearwardly disposed side of the casing I is a panel 20 carrying a jewel bearing within which one end of a shaft 2! is rotatably mounted. The shaft 2| extends through a supporting plate 22 which is mounted at its ends on screws 23 secured to the panel 20. The plate 22 is maintained in spaced relation with respect to the panel 20 by spacing sleeves 24. The shaft 21 is centrally disposed with respect to the casing I, and secured thereto is a pinion 25. The pinion operatively engages with the teeth of a pivoted segment gear 26.

The segment gear is pivotally mounted on a pivot pin at 21 near the periphery of the casing l. The pivot pin mounting the segment gear 26 is held at its ends within suitable jewel bearings carried by the panel 23 and a spaced plate 28 secured to the latter by screws 29. The segment gear at its lower side is provided with a slotted opening which is closed at its upper end by a shoulder piece 26' of hardened steel.

Pivotally mounted at 3!] on a suitable pivot pin is an L-shaped member 3| having an upwardly disposed pointed end engaging with the segment gear 28 at a point on the shoulder piece 26. The pivot pin mounting the L-shaped member 3| is preferably held at its ends within suitable jewel bearings carried by the panel 20 and a spaced plate 32 secured to the latter by screws 33. The L-shaped member 3| at its lower side is preferably provided with a steel insert 31 with which the upwardly disposed pointed tip [3 of the rod ll engages. A substantial part of the combined weight of the -L-shaped member 31 and the segment gear 26 aresupported by the rod I l.

The forward end of the shaft 2| is secured to a circular disc 34 having a plurality of concentric circles 35 marked on its front surface. The circles 35 are each associated with a series of suitable graduation marks or calibrations 36 or other indicia which will indicate in connecn tion with the vertical marking 4 on the window 3 the amount of rotary movement of the disc 34. Each circle 35 with its calibrations 36 is asso ciated with a different predetermined weight I8. Different weights will exert difierent pressures upon an eyeball, and the various concentric circles 35 are each arranged and calibrated with respect to a certain weight. Thus if a given weight is used, the resistance of the eyeball to the pressure exerted thereon by this particular weight will cause the disc 34 to stop at a certain point, and by observing the graduation mark 36 of the particular circle 35 associated with this weight, with respect to the window 3 and the indicating mark 4, the pressure 'on the eyeball with this weight is thereby ascertained.

Any change in the position of the rod Ii, though it be slight, will cause a noticeable rotary movement of the disc 34. In operation the instrument is held by the finger pieces ID in a substantially vertical position with the foot plate l6 resting on the cornea of the eye-ball bein tested as to its intraocular pressure. The end piece l2, by reason of the weight it supports, will exert a definite downward pressure upon that part of the cornea with which its concave end contacts. The end piece 12 will assume a certain depressed position with respect to that part of the cornea immediately surrounding it, and the particular downward movement or depression of said end piece will cause a corresponding rotary movement of the disc 34. The reading on the disc will readily indicate how far the end piece [2 has been depressed in the cornea of the eye-ball. The particular amount of the depression of the end piece l2 will depend primarily upon the resistance offered by the in traocular pressure within the eye-ball.

The downward movement of the end piece I2 and the rod II will allow the L-shaped member 3| to be correspondingly moved about its pivot 3i! in a downward direction by the force of gravity.'-- The consequent lowering of the support of the gear 26 will permit'the force of-gravity to move the latter downwardly about its pivot,

thereby causing the pinion 25, the shaft 2!, and the disc 34 to be simultaneously rotated. The amount of the rotation of the disc 34 will be indicated by observing which of the graduation marks 36 are in registry with or nearest the vertical marking 4 on the window 3.

The slightest movement of the end piece I2 will be readily transferred to the disc to an exaggerated extent by the multiple lever action constituting a part of this invention. In view of the particular arrangement of the disc and its indicia. together with the window and its vertical mark thereon, an operator can readily determine the exact amount of the depression in the eyeball of the end piece I2 with respect to the latters normal initial position.

By slidably mounting the handle means comprising the parts 1, 8, 9 and ID, on the legs 5, the instrument can be conveniently held by an operator in a position whereby substantially its entire weight rests on the eyeball. By so supporting the instrument when an observation is being made, it is assured that the foot plate IE will exert a predetermined and uniform pressure upon an eyeball at each examination.

For convenience in handling the Weight l8 a suitable finger piece [8' is secured .to the side thereof.

Secured to the panel 20 are forwardly projecting stop members 31 which are positioned to intercept the segment gear 26 when it pivotally moves beyond certain limits upwardly or downwardly.

Having described my invention, what I claim 1. In a tonometer, a casing having a window; a plurality of depending parallel legs secured to the casing; a block secured to the lower ends of the legs; a sleeve slidably mounted on each leg; a ring-shaped member secured to and extending around both sleeves; a circular band rotatably carried by the ring-shaped member; a plurality of finger pieces secured to the band; a depending tubular member secured to the block; a foot plate on the tubular member; a reciprocatory rod extending into the casing and through the block and the tubular member; an end piece on the lower end of the rod, the said end piece being adapted to extend below the foot plate when the rod is in a certain position; an L- shaped member pivotally mounted in the casing at a point remote from the center thereof, the said L-shaped member being positioned so a part of its weight is supported by the reciprocating rod; a segment gear having teeth at one side and pivoted at its opposite side at a. point near the side of the casing, the said segment gear being partially supported by the L-shaped member; a pinion rotatably mounted centrally in the casing in mesh with the segment gear; and a disc connected to and adapted to be rotated with the pinion, the said disc having markings thereon which are visible through the window of the casing.

I 2. In a tonometer, a casing having a window; a plurality of depending parallel legs secured to the casing; a block secured to the lower ends of the legs; a sleeve slidably mounted on each leg; handle means joining the sleeves together; a rotatable shaft centrally mounted in the casing; a disc secured to and rotatable with the shaft, having a number of pre-arranged markings thereon which may be visible throughthe window in the casing; a pinion secured to the shaft; asegment gear pivoted in thecasing at a point remote from the shaft and disposed with its teeth in mesh with the pinion; a lever member pivoted at one end inside the casing and disposed in a position supporting the toothed side of the segment gear; a reciprocatory rod extending through the casing and the block. having one end located inside the-casing and disposed so it engagesrwith the lever member and supports the combinedjweight of a part of the lever member and the toothed end of the segment gear a stop member on the rod adapted to engage with the block for preventing the downward movement of the rod beyond certain limits; a depending tubular member secured to the block, having a foot plate thereon, the said tubular member being disposed with the-reciprocatory rod extending therethrough; and an end piece on the lower end of the rod and positioned so it is adapted to project beyond the lower end of the foot plate when the rod approaches the extent of its downward movement.

3.- In a tonometer, a casing having a window; a plurality of depending parallel legs secured to the lower side of the casing; a block secured to the lower ends of the legs; a sleeve slidably mounted on each leg; handle means joining the sleeves together; a rotatable shaft centrally mounted in the casing; a disc secured to and rotatable with the shaft, having a number of pre-arranged markings thereon adapted to be viewed through the window of the casing; a pinion secured to the shaft; a segment gear pivoted in the casing at a point remote from the shaft and disposed with its teeth in mesh with the pinion; a lever member pivoted at one end inside the casing and disposed so as to support the tooth side of the segment gear; a reciprocatory rod extending through the lower side of the casing and through the block, having one end located inside the casing and disposed so it engages with the lever member and supports the combined weight of a part of the lever member and the toothed end of the segment gear; means for preventing the rod from moving beyond certain limits; a depending tubular member secured to the block, having a foot plate thereon, the said tubular member being disposed with the reciprocating rod extending there through; and an end piece on the lower end of the reciprocatory rod and positioned to project beneath the foot plate.

4. In a tonometer, a casing having a, window; a rotatable disc in the casing having pre-arranged markings thereon adapted to be positioned in line with the window when the disc rotates; a plurality of interconnected levers mounted in the casing for rotating the disc; a pair of depending parallel legs secured to the casing; handle means slidably mounted on the legs; a block secured to the legs; a tubular member secured to and extending downwardly from the block; a foot plate on the tubular member; a reciprocatory rod extending in substantially parallel relation to the legs into the tubular member, the block, and the casing, the said rod being disposed in a position whereby a part of the weight of the levers is supported and the disc is rotated in opposite directions in accordance with the reciprocatory movement of the said rod; and an end piece on the lower end of the rod and disposed so it projects beneath the end plate upon the rod approaching the limit of its downward movement.

5. In a tonometer, a casing having a window;

a rotatable disc in the casing having a, series of pre-arranged markings thereon adapted to be viewed through the window; a plurality of legs depending from the casing; handle means slidably mounted 'onthe legs; a block secured to the lower ends of'the legs; a tubular member secured to and depending from the block, having a transparent foot plate at its lower end; a reciprocatory rod extending through the tubular member, the block and into the casing, the rod being so constructed and arranged that its lower end is adapted to project beneath the foot plate when the limit of its downward movement is approached; and means in the casing operatively connecting the upper end of the rod and the disc, whereby the disc is rotated in accordance with the reciprocatory movement of the rod.

6. In a tonometer, a. casing having a window; a rotatable disc in the casing having a series of pre-arranged markings thereon adapted to be viewed through the window; a plurality of sub stantially parallel legs depending from the casing; handle means slidably mounted on the legs; a supporting structure secured to the lower ends of the legs; a tubular member secured to and depending from the supporting structure, having a foot plate at its lower end; a reciprocatory rod extending through the tubular member, the supporting structure and into the casing, the rod being so constructed and arranged that its lower end is adapted to project beneath the foot plate when the limit of its downward movement is approached; means carried by the rod for supporting one or more weights and for engaging with the connecting structure to limit the downward movement of the rod; and means in the casing operatively connecting the upper end of the rod and the disc, whereby the disc is rotated in accordance with the reciprocatory movement of the rod.

7. In a tonometer, a casing having a window; a rotatable indicating means in the casing adapted to be viewed through the window; a plurality of substantially parallel legs depending from the casing; handle means slidably mounted on the legs; a supporting structure secured to the legs having a foot plate thereon; a reciprocatory rod extending upwardly through the foot plate, between the legs and into the casing, the said rod having its lower end so disposed as to project beneath the foot plate when the limit of its downward movement is approached; means for limiting the downward movement of the rod; and means in the casing operatively connecting the upper end of the rod and the indicating means, whereby the indicating means is rotated in accordance with the reciprocatory movement of the rod.

8. In a tonometer, a casing having a window; a rotatable disc in the casing having a series of pre-arranged markings thereon adapted to be viewed through the window; a plurality of substantially parallel and vertical legs depending from the casing; a supporting structure se cured to the legs having a foot plate thereon; handle means slidably mounted on the legs; a, substantially vertical reciprocatory rod extending through the foot plate and into the casing, the said rod having its lower end so disposed as to project beneath the foot plate when the limit of its downward movement is approached; means for limiting the downward movement of the rod; and means in the casing operatively connecting the upper end of the rod and the disc, whereby the disc may be rotated in accordance with the reciprocatory movement of the rod.

9. In a tonometer, a casing having a, sight opening; a disc rotatably mounted in the casing, having markings thereon visible through the sight opening; a depending supporting structure secured to the casing; handle means slidably engaging with the depending structure; an eyeball engaging member carried by the supporting structure; a reciprocating member supported by the supporting structure having its upper end extending into the casing and its lower end projecting through the eyeball engaging member; common means on the reciprocating member for supporting one or more weights and for preventing the downward movement of the reciprocating member beyond certain limits, the said reciprocating member being so arranged that its extreme lower end projects beneath the eyeball engaging member when the said reciprocating member approaches the limit of its downward movement; and means operatively interposed between the disc and the upper end of the reciprocating member for causing-the rotation or the disc in accordance with the reciprocation of the reciprocating member.

10. In a tonometer, a casing, rotatable indicating means mounted in the casing, a depending supporting structure secured to the casing having a transparent eyeball engaging member thereon, handle means slidably engaging with the depending supporting structure, a reciproeating member supported by the supporting structure, having its upper end extending into the casing and its lower end projecting through the transparent eyeball engaging member, the said lower end of the reciprocating member being visible through the transparent eyeball engaging member when in an overlying engaging position with respect to an eyeball being examined, and means operatively interposed between the indicating means and the reciprocating member for causing the rotation of the, said indicating means in accordance with the reciprocation of the reciprocating member.

ALFRED H. PARSONS. 

